A group of 48 weanling Osborne-Mendel rats were fed diets containing 56 percent sucrose. Each rat was caged singly with a donor rate that was infected with Streptococcus mutans 6715-15. The recipients and donors were swabbed twice a week and the bacteria cultured on Mitis Salivarius agar. Every two weeks a subgroup of 12 donors and 12 recipients were sacrificed. The teeth were evaluated for caries and serum and saliva collected for antibody assay. Samples await antibody assay.